Durability tests performed by apparatus such as sliding entry machines or other chair testing apparatus are common. For example, the U.S. patent to Spencer, U.S. Pat. No. 3,592,041, discloses a chair testing apparatus for testing the durability and wear characteristics of a chair. The test apparatus includes a number of weight pads that engages a seat bottom portion and a seat back portion of the chair in a continuous cycling motion.
The U.S. patent to Shaw, U.S. Pat. No. 2,670,627 discloses an apparatus for testing the resistance of textile fabric to abrasion, flexing and creasing.
The U.S. patent to Strand et al., U.S. Pat. No. 5,373,749, discloses a tester for applying forces to a back portion of a vehicle seat.
The U.S. patent to Andrzejak, U.S. Pat. No. 5,379,646 discloses a robotic seat back load-applying device that is capable of applying static and control loading along various points of an automobile seat back.
U.S. patent application entitled "Method and System for Creating a Time-Lapse Record of Wearout of a Part" filed on Oct. 18, 1996 and having U.S. Ser. No. 08/730,897 now abandoned describes a system for durability simulations based upon gross movement of the occupant's buttocks on a seat to be tested. Consequently, the system incompletely represent the human interface to such seats.
Some multi-axis systems rely upon a programmer's expertise in the translation of video images for machine programming of the systems. Such systems also have no feedback loop with which to verify proper simulator loading of the seat.
U.S. Pat. No. 3,841,163 discloses a test dummy indicating system.
U.S. Pat. Nos. 4,873,867; 4,701,132; 4,409,835 and 4,261,113 disclose test dummies that represent the back, buttocks and legs of the human body.
U.S. Pat. No. 4,438,650 discloses a test mannequin which is shaped to correspond to the upper legs, buttocks, and back of a human.
The U.S. patent to Johnson et al., U.S. Pat. No. 5,394,766, discloses a plastic human torso that simulates the size, appearance, and movement of a human torso.
U.S. Pat. No. 5,336,270 discloses a plastic material formed over inner components.
U.S. Pat. No. 3,501,777 discloses a urethane foam disposed over a simulated skeleton.
U.S. Pat. No. 5,376,127 discloses polyethylene sheet material surrounding a endoskeleton.
U.S. Pat. No. 5,166,381 discloses a lower leg cast of thermoplastic material.
U.S. Pat. No. 5,526,707 discloses a simulated pregnant crash test dummy.
U.S. Pat. No. 5,703,303 discloses a simulator for testing seats, with the simulator being mounted on a boom. In particular, the simulator includes a trunk having buttocks and a back hingedly connected thereto so that the back can move independently of the buttocks during extension and retraction of an electric actuator or drive. The drive takes the form of a cylinder, one end of which is pivotally connected to an inner surface of the back. The simulator also includes upper legs or thighs which are pivotally connected to the buttocks by means of ball joints. Each of the thighs is also controllably driven by its own respective electric drive or actuator in the same fashion as the actuator drives the back.
The forces and torques encountered by a robot arm can be measured directly by using a wrist force sensor, which basically consists of a structure with some compliant sections and transducers that measure the deflections of the compliant sections. The most common transducer used for this purpose is the strain gage, others being piezoelectric, magnetostrictive, magnetic, and so on. For example, the U.S. patent to Giovinazzo et al., U.S. Pat. No. 4,320,392, discloses a transducer which has six degrees of freedom and is arranged to output electrical signals indicative of the forces and movements applied thereto.
Forces and torques can also be sensed indirectly by measuring the forces acting on the joints of a manipulator. For joints driven by DC electric motors, the force is directly proportional to the armature current; for joints driven by hydraulic motors, it is proportional to back pressure.
Some scientific studies of human movement have relied on markers affixed to the body of the subject. These markers can then be tracked over time to reveal the patterns of movement of various parts of the body.
Marking points of interest such as the joints of the body is only the first step in analyzing human movement. Before any analysis can occur, the markers must be detected and their position measured. Such measurement can be tedious and time-consuming. For example, athletes participating in early film studies of human motion wore X's on their joints while throwing a football or carrying out some other athletic task. Researchers then went through the films frame by frame, digitizing the positions of the X markers to get the data required to analyze force, acceleration, and so on.
The measurement of marker position has been automated in various ways. One example is the approach described in the U.S. patent to Thornton, U.S. Pat. No. 4,375,674. Thornton's kinesimetric apparatus relies upon one or more incandescent lamps affixed to the subject's body as markers. The 3-D position of each marker is determined through triangulation, given the output signals of a number of video cameras focused on the subject. This makes it possible to build up a movement envelope over time for each marker.
The use of marker shape to provide 3-D information without triangulation or multiple sensors is proposed by the U.S. patent to Spackova et al., U.S. Pat. No. 4,539,585. An equilateral triangle is affixed to a subject who is to be photographed by a video camera. As the subject turns from side-to-side, the apparent shape of the triangle will change. A computer determines orientation from the amount of changes.
What all of these approaches have in common is the use of markers or signal sources which are worn or held by the person whose movements are being measured.
A number of other devices exist which rely on a human operator to identify features of interest after the fact. In such a system, the subject wears no markers while his or her image is being recorded. Instead, an operator marks the specified features by using a light pen or similar device.
The U.S. patent to Dewar, Jr. et al., U.S. Pat. No. 4,254,433, discloses a visual motion tracking system wherein movement of an article is monitored by providing a patterned target to move with the object. A solid state line scan camera views the pattern of the target as it moves relative to the camera and the electronic output of the camera representing the light and dark areas of the target is analyzed by an electronic circuit to determine the movement of the target and therefore of the object being monitored. The resulting electronic signal representing the motion of the object is useful for coordinating the movement of a robot which is operating upon the object during its movement.
Qualisys, Inc. of Glastonbury, Conn. sells a kinematic measurement product called a PC Reflex 3D 60 Motion Measurements System. The system is designed to measure the motion of subjects in real-time and produce both qualitative and quantitative results within a matter of seconds. The system includes the following components:
1. Multiple position sensors (camera systems) each of which includes a specially designed video camera and a specially designed video processor. PA1 2. Software which enables the user to set up a desired field of view of the position sensors, calibrate the desired field of view, and process in real-time the measured spatial coordinates (x,y) of target markers which are attached to a subject in the calibrated field of view. PA1 3. Passive reflective target markers--come in various sizes and shapes. Standard Scotchlite 3M.TM. reflective paint can also be used. PA1 4. A calibration frame which is used so that the volume of the desired field of view can be calibrated using software calibration routines.
Seat force sensors embedded within a seat to obtain electrical signals representative of force or weight experienced at various locations on the seat are well known. For example, the U.S. patent to Blackburn et al., U.S. Pat. No. 5,232,243, discloses film-like occupant position and weight sensors.
The U.S. patent to Schousek, U.S. Pat. No. 5,474,327, discloses a seat pressure sensor comprising eight variable resistance pressure sensors embedded in a seat cushion. The response of each sensor to occupant pressure is monitored by a microprocessor which calculates total weight and weight distribution.